The present invention relates to apparatus for reading, writing and storing bit-encoded data, and more particularly to disk drives including packs of multiple, concentrically stacked disks.
The continuing effort to increase data storage capacities of magnetic disk drives and other data storage devices is concerned largely with increasing the density at which data can be stored on the available recording surface area. Another approach involves mounting multiple magnetic disks on a single spindle assembly in which the disks are stacked in integral, spaced apart and concentric relation. Such spindle assemblies typically include an elongate shaft, a hub fixed to the shaft and supporting the disks, and bearings and bushings at opposed ends of the shaft, to support the shaft, hub and disks for rotation relative to the disk drive housing. Also mounted movably with respect to the housing is an actuator, either of the rotary or linear type, for selectively positioning data transducing heads relative to the disks.
The design and manufacture of such drives involve disparate and often competing needs. The preferred high data storage densities require precision alignment of the disk pack and actuator, stability during rotation of the spindle assembly and resistance to thermal effects due to differing thermal expansion coefficients of materials employed in the drive. The housing must be strong, lightweight, resistant to vibration and provide an effective seal to prevent contamination of the housing interior, particularly in the region of the disks. At the same time, cost considerations stimulate efforts to reduce the number of parts and steps involved in assembling disk drives.
Among the many approaches for meeting these needs is a divided housing for magnetic disks disclosed in U.S. Pat. No. 4,899,237 (Tochiyama et al). The housing includes a shell which supports both a magnetic disk pack and a rotary actuator, and a cover that closes an opening in the shell. Holes that support bushings at opposite ends of the spindle shaft are drilled through opposite side walls of the shell in a single operation, and thus are precision aligned. The rotary actuator has a shaft which is similarly mounted by precision aligned holes in the shell. This arrangement is said to enhance the mechanical rigidity of the disk pack and actuator mountings, and improve sealing.
U.S. Pat. No. 4,835,637 (Mach et al) discloses a disk file in which a disk stack sub-assembly is mounted within a housing. A shaft of the sub-assembly is mounted to the housing through upper and lower bearings and associated upper and lower bearing supports. The lower bearing support is movable axially with respect to the outer race of the lower bearing. A spring biases the lower bearing support axially upward relative to the lower bearing outer race. This arrangement enables reduction of the sub-assembly length to enable its insertion between opposed parallel walls of the disk file housing.
While the above approaches have met with limited success, there remains a need to provide a disk drive capable of storing data at relatively high densities, and at low cost.
Therefore, it is an object of the present invention to provide a disk drive housing which is strong, lightweight and resistant to vibration and thermal effects.
Another object is to provide a spindle assembly for a disk drive including means for mounting a spindle shaft for rotation relative to a disk drive housing, which means are particularly well suited to facilitate assembly into a unitary housing.
A further object of the invention is to provide, in a spindle assembly with an internal motor, an effective system for purging air in the region of disks, and seal against contamination of the region of the disks from particulates generated near the motor and bearings.
Yet another object of the invention is to provide a mounting interface for a spindle assembly and disk drive housing, in which a rotatable spindle shaft is precisely aligned as it is installed into the housing, without jigs or other extraneous alignment tooling.